Method of manufacturing semiconductor device, substrate processing apparatus, and recording medium

ABSTRACT

There is provided a technique, including: (a) forming NH termination on a surface of a substrate by supplying a first reactant containing N and H to the substrate; (b) forming a first SiN layer having SiCl termination formed on its surface by supplying SiCl4 as a precursor to the substrate to react the NH termination formed on the surface of the substrate with the SiCl4; (c) forming a second SiN layer having NH termination formed on its surface by supplying a second reactant containing N and H to the substrate to react the SiCl termination formed on the surface of the first SiN layer with the second reactant; and (d) forming a SiN film on the substrate by performing a cycle a predetermined number of times under a condition where the SiCl4 is not gas-phase decomposed after performing (a), the cycle including non-simultaneously performing (b) and (c).

CROSS-REFERENCE TO RELATED APPLICATION

This non-provisional U.S. patent application is a continuation of U.S.patent application Ser. No. 16/988,235, filed on Aug. 7, 2020, which isa continuation of U.S. patent application Ser. No. 16/286,292, filed onFeb. 26, 2019, which issued as U.S. Pat. No. 10,770,287 on Sep. 8, 2020,and claims the benefit of priority from Japanese Patent Application No.2018-034770, filed on Feb. 28, 2018, the entire contents of which areincorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a method of manufacturing asemiconductor device, a substrate processing apparatus, and a recordingmedium.

BACKGROUND

In a related art, as an example of a process of manufacturing asemiconductor device, a process of forming a film containing silicon(Si) and nitrogen (N), i.e., a silicon nitride film (SiN film), on asubstrate is carried out.

SUMMARY

The present disclosure provides some embodiments of a technique thatimproves film thickness uniformity of a SiN film formed on a substratein a plane of the substrate.

According to an embodiment of the present disclosure, there is provideda technique, which includes: (a) forming NH termination on a surface ofa substrate by supplying a first reactant containing N and H to thesubstrate; (b) forming a first SiN layer having SiCl termination formedon its surface by supplying SiCl₄ as a precursor to the substrate toreact the NH termination formed on the surface of the substrate with theSiCl₄; (c) forming a second SiN layer having NH termination formed onits surface by supplying a second reactant containing N and H to thesubstrate to react the SiCl termination formed on the surface of thefirst SiN layer with the second reactant; and (d) forming a SiN film onthe substrate by performing a cycle a predetermined number of timesunder a condition where the SiCl₄ is not gas-phase decomposed afterperforming (a), the cycle including non-simultaneously performing (b)and (c).

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic configuration diagram of a vertical type processfurnace of a substrate processing apparatus suitably used in anembodiment of the present disclosure, in which a portion of the processfurnace is shown in a vertical cross sectional view.

FIG. 2 is a schematic configuration diagram of a vertical type processfurnace of the substrate processing apparatus suitably used in anembodiment of the present disclosure, in which a portion of the processfurnace is shown in a cross sectional view taken along line A-A in FIG.1.

FIG. 3 is a schematic configuration diagram of a controller of thesubstrate processing apparatus suitably used in one embodiment of thepresent disclosure, in which a control system of a controller is shownin a block diagram.

FIG. 4 is a diagram illustrating a film-forming sequence according to anembodiment of the present disclosure.

FIG. 5A illustrates a partial enlarged view of a surface of a substrateafter a first reactant is supplied, FIG. 5B illustrates a partialenlarged view of a surface of a substrate after a precursor is supplied,and FIG. 5C illustrates a partial enlarged view of a surface of asubstrate after a second reactant is supplied.

FIG. 6A is a diagram illustrating an evaluation result of film thicknessuniformity of a SiN film formed on a substrate in a plane of thesubstrate, and FIG. 6B is a diagram illustrating an evaluation result ofprocessing resistance of a SiN film formed on the substrate.

FIG. 7 is a diagram illustrating an evaluation result of film thicknessuniformity of a SiN film formed on a substrate in the plane of thesubstrate.

DETAILED DESCRIPTION One Embodiment of the Present Disclosure

An embodiment of the present disclosure will now be described in detailmainly with reference to FIGS. 1 to 5C.

(1) Configuration of the Substrate Processing Apparatus

As illustrated in FIG. 1, a process furnace 202 includes a heater 207 asa heating mechanism (temperature adjustment part). The heater 207 has acylindrical shape and is supported by a holding plate so as to bevertically installed. The heater 207 functions as an activationmechanism (an excitation part) configured to thermally activate (excite)a gas.

A reaction tube 203 is disposed inside the heater 207 to be concentricwith the heater 207. The reaction tube 203 is made of a heat resistantmaterial, e.g., quartz (SiO₂), silicon carbide (SiC) or the like, andhas a cylindrical shape with its upper end closed and its lower endopened. A process chamber 201 is formed in a hollow cylindrical portionof the reaction tube 203. The process chamber 201 is configured toaccommodate wafers 200 as substrates. The processing of the wafers 200is performed in the process chamber 201.

Nozzles 249 a and 249 b are installed in the process chamber 201 so asto penetrate a lower sidewall of the reaction tube 203. Gas supply pipes232 a and 232 b are respectively connected to the nozzles 249 a and 249b.

Mass flow controllers (MFCs) 241 a and 241 b, which are flow ratecontrollers (flow rate control parts), and valves 243 a and 243 b, whichare opening/closing valves, are installed in the gas supply pipes 232 aand 232 b sequentially from the corresponding upstream sides of gasflow, respectively. Gas supply pipes 232 c and 232 d are respectivelyconnected to the gas supply pipes 232 a and 232 b at the downstream sideof the valves 243 a and 243 b. MFCs 241 c and 241 d and valves 243 c and243 d are respectively installed in the gas supply pipes 232 c and 232 dsequentially from the corresponding upstream sides of gas flow.

As illustrated in FIG. 2, the nozzles 249 a and 249 b are disposed in aspace with an annular plan-view shape between the inner wall of thereaction tube 203 and the wafers 200 such that the nozzles 249 a and 249b extend upward along an arrangement direction of the wafers 200 from alower portion of the inner wall of the reaction tube 203 to an upperportion of the inner wall of the reaction tube 203. Specifically, thenozzles 249 a and 249 b are installed at a lateral side of a waferarrangement region in which the wafers 200 are arranged, namely in aregion which horizontally surrounds the wafer arrangement region, so asto extend along the wafer arrangement region. Gas supply holes 250 a and250 b for supplying a gas are installed on the side surfaces of thenozzles 249 a and 249 b, respectively. The gas supply holes 250 a and250 b are opened toward the center of the reaction tube 203 so as toallow a gas to be supplied toward the wafers 200. The gas supply holes250 a and 250 b may be formed in a plural number between the lowerportion of the reaction tube 203 and the upper portion of the reactiontube 203.

A precursor (precursor gas), for example, a chlorosilane-based gas whichcontains silicon (Si) and chlorine (Cl), is supplied from the gas supplypipe 232 a into the process chamber 201 via the MFC 241 a, the valve 243a, and the nozzle 249 a. The precursor gas refers to a gaseousprecursor, for example, a gas obtained by vaporizing a precursor whichremains in a liquid state under a room temperature and an atmosphericpressure, or a precursor which remains in a gas state under a roomtemperature and an atmospheric pressure. As the chlorosilane-based gas,it may be possible to use, for example, a tetrachlorosilane (SiCl₄) gas.The SiCl₄ gas contains four chemical bonds (Si—Cl bonds) of Si and Cl inone molecule.

A hydrogen nitride-based gas containing, for example, nitrogen (N) andhydrogen (H), as first and second reactants, is supplied from the gassupply pipe 232 b into the process chamber 201 via the MFC 241 b, thevalve 243 b, and the nozzle 249 b. As the hydrogen nitride-based gas, itmay be possible to use, for example, an ammonia (NH₃) gas. The NH₃ gascontains three chemical bonds (N—H bonds) of N and H in one molecule.

A nitrogen (N₂) gas as an inert gas is supplied from the gas supplypipes 232 c and 232 d into the process chamber 201 via the MFCs 241 cand 241 d, the valves 243 c and 243 d, the gas supply pipes 232 a and232 b, and the nozzles 249 a and 249 b. The N₂ gas acts as a purge gas,a carrier gas, a dilution gas, or the like.

A precursor supply system includes the gas supply pipe 232 a, the MFC241 a, and the valve 243 a. A reactant supply system (first and secondreactant supply systems) includes the gas supply pipe 232 b, the MFC 241b, and the valve 243 b. An inert gas supply system includes the gassupply pipes 232 c and 232 d, the MFCs 241 c and 241 d, and the valves243 c and 243 d.

One or all of various supply systems described above may be configuredas an integrated supply system 248 in which the valves 243 a to 243 d,the MFCs 241 a to 241 d, and the like are integrated. The integratedsupply system 248 is connected to each of the gas supply pipes 232 a to232 d so that a supply operation of various kinds of gases into the gassupply pipes 232 a to 232 d, i.e., an opening/closing operation of thevalves 243 a to 243 d, a flow rate adjusting operation by the MFCs 241 ato 241 d or the like, is controlled by a controller 121 which will bedescribed later. The integrated supply system 248 is configured as anintegral type or division type integrated unit, and is also configuredso that it is detachable from the gas supply pipes 232 a to 232 d or thelike, so as to perform maintenance, replacement, expansion or the likeof the integrated supply system 248, on an integrated unit basis.

An exhaust pipe 231 configured to exhaust an internal atmosphere of theprocess chamber 201 is installed at a lower side of the sidewall of thereaction tube 203. A vacuum pump 246 as a vacuum exhaust device isconnected to the exhaust pipe 231 via a pressure sensor 245 as apressure detector (pressure detection part) which detects the internalpressure of the process chamber 201 and an auto pressure controller(APC) valve 244 as a pressure regulator (pressure regulation part). TheAPC valve 244 is configured so that a vacuum exhaust of the interior ofthe process chamber 201 and a vacuum exhaust stop can be performed byopening and closing the APC valve 244 while operating the vacuum pump246 and so that the internal pressure of the process chamber 201 can beadjusted by adjusting an opening degree of the APC valve 244 based onpressure information detected by the pressure sensor 245 while operatingthe vacuum pump 246. An exhaust system includes the exhaust pipe 231,the pressure sensor 245 and the APC valve 244. The vacuum pump 246 maybe regarded as being included in the exhaust system.

A seal cap 219, which serves as a furnace opening cover configured tohermetically seal a lower end opening of the reaction tube 203, isinstalled under the reaction tube 203. The seal cap 219 is made of ametal material such as, e.g., stainless steel (SUS) or the like, and isformed in a disc shape. An O-ring 220, which is a seal member makingcontact with the lower end portion of the reaction tube 203, isinstalled on an upper surface of the seal cap 219. A rotation mechanism267 configured to rotate a boat 217, which will be described later, isinstalled under the seal cap 219. A rotary shaft 255 of the rotationmechanism 267, which penetrates the seal cap 219, is connected to theboat 217. The rotation mechanism 267 is configured to rotate the wafers200 by rotating the boat 217. The seal cap 219 is configured to bevertically moved up and down by a boat elevator 115 which is an elevatormechanism installed outside the reaction tube 203. The boat elevator 215is configured as a transfer device (transfer mechanism) which loads andunloads (transfers) the wafers 210 into and from (out of) the processchamber 201 by moving the seal cap 219 up and down.

The boat 217 serving as a substrate support is configured to support aplurality of wafers 200, e.g., 25 to 200 wafers, in such a state thatthe wafers 200 are arranged in a horizontal posture and in multiplestages along a vertical direction with the centers of the wafers 200aligned with one another. That is, the boat 217 is configured to arrangethe wafers 200 in a spaced-apart relationship. The boat 217 is made of aheat resistant material such as quartz or SiC. Heat insulating plates218 made of a heat resistant material such as quartz or SiC areinstalled below the boat 217 in a horizontal posture and in multiplestages.

A temperature sensor 263 serving as a temperature detector is installedin the reaction tube 203. Based on temperature information detected bythe temperature sensor 263, a state of supplying electric power to theheater 207 is adjusted such that the interior of the process chamber 201has a desired temperature distribution. The temperature sensor 263 isinstalled along the inner wall of the reaction tube 203.

As illustrated in FIG. 3, the controller 121, which is a control part(control means), may be configured as a computer including a centralprocessing unit (CPU) 121 a, a random access memory (RAM) 121 b, amemory device 121 c, and an I/O port 121 d. The RAM 121 b, the memorydevice 121 c and the I/O port 121 d are configured to exchange data withthe CPU 121 a via an internal bus 121 e. An input/output device 122formed of, e.g., a touch panel or the like, is connected to thecontroller 121.

The memory device 121 c is configured by, for example, a flash memory, ahard disk drive (HDD), or the like. A control program for controllingoperations of a substrate processing apparatus, a process recipe forspecifying sequences and conditions of a film-forming process asdescribed hereinbelow, or the like is readably stored in the memorydevice 121 c. The process recipe functions as a program for causing thecontroller 121 to execute each sequence in the film-forming process, asdescribed hereinbelow, to obtain a predetermined result. Hereinafter,the process recipe and the control program will be generally and simplyreferred to as a “program.” Furthermore, the process recipe will besimply referred to as a “recipe.” When the term “program” is usedherein, it may indicate a case of including only the recipe, a case ofincluding only the control program, or a case of including both therecipe and the control program. The RAM 121 b is configured as a memoryarea (work area) in which a program, data and the like read by the CPU121 a is temporarily stored.

The I/O port 121 d is connected to the MFCs 241 a to 241 d, the valves243 a to 243 d, the pressure sensor 245, the APC valve 244, the vacuumpump 246, the temperature sensor 263, the heater 207, the rotationmechanism 267, the boat elevator 115, and the like, as described above.

The CPU 121 a is configured to read the control program from the memorydevice 121 c and execute the same. The CPU 121 a also reads the recipefrom the memory device 121 c according to an input of an operationcommand from the input/output device 122. In addition, the CPU 121 a isconfigured to control, according to the contents of the recipe thusread, the flow rate adjusting operation of various kinds of gases by theMFCs 241 a to 241 d, the opening/closing operation of the valves 243 ato 243 d, the opening/closing operation of the APC valve 244, thepressure regulating operation performed by the APC valve 244 based onthe pressure sensor 245, the driving and stopping of the vacuum pump246, the temperature adjusting operation performed by the heater 207based on the temperature sensor 263, the operation of rotating the boat217 with the rotation mechanism 267 and adjusting the rotation speed ofthe boat 217, the operation of moving the boat 217 up and down with theboat elevator 115, and the like.

The controller 121 may be configured by installing, on the computer, theaforementioned program stored in an external memory device 123. Theexternal memory device 123 may include, for example, a magnetic discsuch as an HDD, an optical disc such as a CD, a magneto-optical discsuch as an MO, a semiconductor memory such as a USB memory, and thelike. The memory device 121 c or the external memory device 123 isconfigured as a computer-readable recording medium. Hereinafter, thememory device 121 c and the external memory device 123 will be generallyand simply referred to as a “recording medium.” When the term “recordingmedium” is used herein, it may indicate a case of including only thememory device 121 c, a case of including only the external memory device123, or a case of including both the memory device 121 c and theexternal memory device 123. Furthermore, the program may be supplied tothe computer using a communication means such as the Internet or adedicated line, instead of using the external memory device 123.

(2) Substrate Processing

A substrate processing sequence example of forming a SiN film on a wafer200 as a substrate using the aforementioned substrate processingapparatus, i.e., a film-forming sequence example, which is one of theprocesses for manufacturing a semiconductor device, will be describedwith reference to FIG. 4. In the following descriptions, the operationsof the respective parts constituting the substrate processing apparatusare controlled by the controller 121.

In the film-forming sequence illustrated in FIG. 4, there are performed:step A of supplying an NH₃ gas as a first reactant containing N and H toa wafer 200 to form NH termination on a surface of the wafer 200; step Bof supplying a SiCl₄ gas as a precursor to the wafer 200 to react the NHtermination formed on the surface of the wafer 200 with SiCl₄ to form afirst SiN layer having SiCl termination formed on its surface; and stepC of supplying an NH₃ gas as a second reactant containing N and H to thewafer 200 to react the SiCl termination formed on the surface of thefirst SiN layer with the NH₃ gas to form a second SiN layer having NHtermination formed on its surface.

Specifically, a cycle which non-simultaneously performs step B and stepC described above under a condition in which SiCl₄ is not gas-phasedecomposed after performing step A described above is implemented apredetermined number of times. Thus, a SiN film is formed on the wafer200. Furthermore, in FIG. 4, execution periods of steps A, B, and C aredenoted as A, B, and C, respectively.

In the present disclosure, for the sake of convenience, the film-formingsequence illustrated in FIG. 4 may sometimes be denoted as follows. Thesame denotation will be used in other embodiments and the like asdescribed hereinbelow.

NH₃→(SiCl₄→NH₃)×n=>SiN

When the term “wafer” is used herein, it may refer to a wafer itself ora laminated body of a wafer and a predetermined layer or film formed onthe surface of the wafer. In addition, when the phrase “a surface of awafer” is used herein, it may refer to a surface of a wafer itself or asurface of a predetermined layer or the like formed on a wafer.Furthermore, in the present disclosure, the expression “a predeterminedlayer is formed on a wafer” may mean that a predetermined layer isdirectly formed on a surface of a wafer itself or that a predeterminedlayer is formed on a layer or the like formed on a wafer. In addition,when the term “substrate” is used herein, it may be synonymous with theterm “wafer.”

(Wafer Charging and Boat Loading)

A plurality of wafers 200 is charged on the boat 217 (wafer charging).Thereafter, as illustrated in FIG. 1, the boat 217 supporting theplurality of wafers 200 is lifted up by the boat elevator 115 and isloaded into the process chamber 201 (boat loading). In this state, theseal cap 219 seals the lower end of the reaction tube 203 through theO-ring 220.

(Pressure Regulation and Temperature Adjustment)

The interior of the process chamber 201, namely the space in which thewafers 200 are located, is vacuum-exhausted (depressurization-exhausted)by the vacuum pump 246 so as to reach a desired processing pressure(degree of vacuum). In this operation, the internal pressure of theprocess chamber 201 is measured by the pressure sensor 245. The APCvalve 244 is feedback-controlled based on the measured pressureinformation. Furthermore, the wafers 200 in the process chamber 201 areheated by the heater 207 to a desired processing temperature(film-forming temperature). In this operation, the state of supplyingelectric power to the heater 207 is feedback-controlled based on thetemperature information detected by the temperature sensor 263 such thatthe interior of the process chamber 201 has a desired temperaturedistribution. In addition, the rotation of the wafers 200 by therotation mechanism 267 begins. The driving of the vacuum pump 246 andthe heating and rotation of the wafers 200 may be all continuouslyperformed at least until the processing of the wafers 200 is completed.

(Film-Forming Process)

Next, the following steps A and B are sequentially performed.

[Step A]

At this step, an NH₃ gas is supplied to the wafer 200 in the processchamber 201. Specifically, the valve 243 b is opened to allow an NH₃ gasto flow through the gas supply pipe 232 b. The flow rate of the NH₃ gasis adjusted by the MFC 241 b. The NH₃ gas is supplied into the processchamber 201 via the nozzle 249 b and is exhausted from the exhaust pipe231. At this time, the NH₃ gas is supplied to the wafer 200 from theside of the wafer 200. Simultaneously, the valves 243 c and 243 d may beopened to allow an N₂ gas to flow through the gas supply pipes 232 c and232 d.

The processing conditions at this step may be exemplified as follows:

NH₃ gas supply flow rate: 100 to 10,000 sccm

N₂ gas supply flow rate (per gas supply pipe): 0 to 10,000 sccm

Supply time of each gas: 1 to 30 minutes

Processing temperature: 300 to 1,000 degrees C., 700 to 900 degrees C.in some embodiments, or 750 to 800 degrees C. in some embodiments

Processing pressure: 1 to 4,000 Pa or 20 to 1,333 Pa in someembodiments.

Furthermore, in the present disclosure, the expression of the numericalrange such as “300 to 1,000 degrees C.” may mean that a lower limitvalue and an upper limit value are included in that range. Therefore,“300 to 1,000 degrees C.” may mean “300 degrees C. or higher and 1,000degrees C. or lower”. The same applies to other numerical ranges.

A natural oxide film or the like may be formed on the surface of thewafer 200 prior to performing a film-forming process. By supplying theNH₃ gas to the wafer 200 under the aforementioned conditions, NHtermination can be formed on the surface of the wafer 200 on which thenatural oxide film or the like is formed. Thus, a desired film-formingreaction can go ahead on the wafer 200 at step B as describedhereinbelow. A partial enlarged view of the surface of the wafer 200 onwhich the NH termination is formed is illustrated in FIG. 5A. The NHtermination formed on the surface of the wafer 200 may be regarded assynonymous with an H termination. Furthermore, since the supply of theNH₃ gas to the wafer 200 and the process of forming the NH terminationon the surface of the wafer 200 at this step are performed prior to asubstantial film-forming process (steps B and C), they will be referredto as pre-flow and pre-processing, respectively.

In the case where the NH₃ gas is supplied to the wafer 200 from the sideof the wafer 200 as in the present embodiment, there is a tendency thatthe formation of the NH termination starts earlier in an outerperipheral portion of the wafer 200, and starts in the central portionof the wafer 200 with delay. This phenomenon becomes particularlyconspicuous when a pattern including a recess such as a trench or a holeis formed on the surface of the wafer 200. At this step, if the supplytime of the NH₃ gas is less than 1 minute, although the NH terminationmay be formed in the outer peripheral portion of the wafer 200, the NHtermination may be difficult to be formed in the center portion of thewafer 200. By setting the supply time of the NH₃ gas at a time of 1minute or more, it is possible to form the NH termination from the outerperipheral portion to the central portion of the wafer 200 uniformly,i.e., substantially uniformly in amount and density. However, if thesupply time of the NH₃ gas exceeds 30 minutes, the supply of the NH₃ gasto the wafer 200 may be continued in a state in which the formationreaction of the NH termination on the surface of the wafer 200 issaturated. As a result, usage amount of the NH₃ gas which does notcontribute to the formation of the NH termination unnecessarilyincreases, which may increase a gas cost. By setting the supply time ofthe NH₃ gas at a time of 30 minutes or less, it is possible to suppressan increase in the gas cost.

After the NH termination is formed on the surface of the wafer 200 bypre-flowing the NH₃ gas to the wafer 200, the valve 243 b is closed tostop the supply of the NH₃ gas into the process chamber 201. Then, theinterior of the process chamber 201 is vacuum-exhausted and the gas orthe like remaining within the process chamber 201 is removed from theinterior of the process chamber 201. At this time, the valves 243 c and243 d are opened to supply an N₂ gas as a purge gas into the processchamber 201 (purge step). The processing pressure at the purge step maybe set at a pressure of, for example, 1 to 100 Pa, and the supply flowrate of the N₂ gas may be set at a flow rate of, for example, 10 to10,000 sccm.

As the first reaction gas, it may be possible to use, in addition to theNH₃ gas, a hydrogen nitride-based gas such as a diazene (N₂H₂) gas, ahydrazine (N₂H₄) gas, and an N₃H₈ gas.

As the inert gas, it may be possible to use, in addition to the N₂ gas,a rare gas such as an Ar gas, an He gas, an Ne gas, and an Xe gas. Thisalso applies to steps B and C as described hereinbelow.

[Step B]

At this step, a SiCl₄ gas is supplied to the wafer 200 in the processchamber 201, namely the NH termination formed on the surface of thewafer 200. Specifically, the opening/closing control of the valves 243a, 243 c and 243 d is performed in the same procedure as theopening/closing control of the valves 243 b to 243 d at step A. The flowrate of the SiCl₄ gas is controlled by the MFC 241 a. The SiCl₄ gas issupplied into the process chamber 201 via the nozzle 249 a and isexhausted from the exhaust pipe 231. At this time, the SiCl₄ gas issupplied to the wafer 200 from the side of the wafer 200.

The processing conditions at this step may be exemplified as follows:

SiCl₄ gas supply flow rate: 10 to 2,000 sccm, or 100 to 1,000 sccm insome embodiments

Supply time of SiCl₄ gas: 60 to 180 seconds, or 60 to 120 seconds insome embodiments

Processing temperature: 300 to 1,000 degrees C., 700 to 900 degrees C.in some embodiments, or 750 to 800 degrees C. in some embodiments

Processing pressure: 1 to 2,000 Pa, or 20 to 1,333 Pa in someembodiments.

Other processing conditions may be similar to the processing conditionsof step A.

By supplying the SiCl₄ gas to the wafer 200 under the aforementionedconditions, it is possible to react the NH termination formed on thesurface of the wafer 200 with SiCl₄. Specifically, at least a portion ofSi—Cl bonds in SiCl₄ and at least a portion of N—H bonds in the NHtermination formed on the surface of the wafer 200 can be broken.Furthermore, Si after the at least a portion of Si—Cl bonds in SiCl₄ arebroken can be bonded to N after the at least a portion of N—H bonds inthe NH termination formed on the surface of the wafer 200 are broken toform Si—N bonds. Cl separated from Si and H separated from Nrespectively constitute gaseous substances such as HCl or the like so asto be desorbed from the wafer 200 and are exhausted from the exhaustpipe 231.

In addition, at this step, the Si—Cl bonds, which are not converted intothe Si—N bonds among the Si—Cl bonds in SiCl₄ during the aforementionedreaction, can be held without being broken. That is, at this step, Siafter the at least a portion of Si—Cl bonds in SiCl₄ are broken can bebonded to N after the at least a portion of N—H bonds in the NHtermination formed on the surface of the wafer 200 are broken in a statewhere Cl is bonded to each of three bonding hands of four bonding handsof Si constituting SiCl₄.

In the present disclosure, the aforementioned reaction proceeding on thesurface of the wafer 200 at step B will be referred to as an adsorptivesubstitution reaction. At this step, the adsorptive substitutionreaction described above can go ahead to form a layer which contains Siand N and whose entire surface is terminated with SiCl, i.e., a siliconnitride layer (first SiN layer) having SiCl termination formed on itssurface, on the wafer 200. A partial enlarged view of the surface of thewafer 200 on which the first SiN layer having SiCl termination formed onits surface is formed is illustrated in FIG. 5B. Furthermore, in FIG.5B, illustration of part of Cl is omitted for the sake of convenience.The first SiN layer having SiCl termination formed on its surfacebecomes a layer in which further Si deposition on the wafer 200 does notgo ahead even if the supply of the SiCl₄ gas to the wafer 200 is furthercontinued after the formation of this layer, due to Cl constituting theSiCl termination acting as steric hindrance. That is, the first SiNlayer having SiCl termination formed on its surface becomes a layer towhich self-limitation is applied for further Si adsorption reaction.Accordingly, the thickness of the first SiN layer becomes a uniformthickness of less than one atomic layer (less than one molecular layer)over the entire region in the plane of the wafer. Furthermore, the SiCltermination formed on the surface of the wafer 200 may be regarded assynonymous with a Cl termination.

The processing conditions at this step are conditions under which SiCl₄supplied into the process chamber 201 is not gas-phase decomposed(pyrolyzed). That is, the aforementioned processing conditions areconditions under which SiCl₄ supplied into the process chamber 201 doesnot generate an intermediate in the gas phase and the Si deposition onthe wafer 200 by the gas-phase reaction does not go ahead. In otherwords, the processing conditions described above are conditions underwhich only the adsorptive substitution reaction described above canoccur on the wafer 200. By setting the processing conditions at thisstep to such conditions, it is possible to allow the first SiN layerformed on the wafer 200 to become a layer having excellent thicknessuniformity in the plane of the wafer (hereinafter, also simply referredto as in-plane thickness uniformity).

If the film-forming temperature (processing temperature) is lower than300 degrees C., there may be a case where it is difficult for the firstSiN layer to be formed on the wafer 200 and for the formation of the SiNfilm on the wafer 200 to go ahead at a practical deposition rate.Furthermore, a large amount of impurity such as Cl or the like mayremain in the SiN film formed on the wafer 200, lowering a processingresistance of the SiN film. By setting the film-forming temperature at atemperature of 300 degree C. or higher, the formation of the SiN film onthe wafer 200 can go ahead at a practical deposition rate. In addition,it is possible to allow the SiN film formed on the wafer 200 to become afilm having low impurity concentration and excellent processingresistance. By setting the film-forming temperature at a temperature of700 degrees C. or higher, it is possible to reliably achieve theaforementioned effects. By setting the film-forming temperature at atemperature of 750 degrees C. or higher, it is possible to more reliablyachieve the aforementioned effects.

If film-forming temperature exceeds 1,000 degrees C., there may be acase where a reaction other than the aforementioned adsorptivesubstitution reaction goes ahead in the process chamber 201. Forexample, the Si—Cl bonds which are not converted into the Si—N bondsamong the Si—Cl bonds in SiCl₄ may be broken, making it difficult to beSiCl-terminated on the entire surface of the first SiN layer. That is,it may be difficult for the first SiN layer to become a layer to whichself-limitation is applied for further Si adsorption reaction. Inaddition, SiCl₄ supplied into the process chamber 201 is gas-phasedecomposed (pyrolyzed) to generate an intermediate, and the Sideposition on the wafer 200 by the gas-phase reaction may go ahead. As aresult, the in-plane thickness uniformity of the first SiN layer formedon the wafer 200, i.e., the film thickness uniformity of the SiN film inthe plane of the substrate (hereinafter, simply referred to as in-planefilm thickness uniformity), may be deteriorated. By setting thefilm-forming temperature at a temperature of 1,000 degrees C. or lower,it is possible to solve the problems described above. By setting thefilm-forming temperature at a temperature of 900 degrees C. or lower, itis possible to reliably solve the problems described above. By settingthe film-forming temperature at a temperature of 800 degrees C. orlower, it is possible to more reliably solve the problems describedabove.

From these facts, it is desirable that the film-forming temperature beset at 300 to 1,000 degrees C., 700 to 900 degrees C. in someembodiments, or 750 to 800 degrees C. in some embodiments. Furthermore,among the temperature conditions illustrated above, the relatively hightemperature condition such as, e.g., 700 to 900 degrees C., is atemperature condition under which a chlorosilane-based gas such as adichlorosilane (SiH₂Cl₂, abbreviation: DCS) gas, a hexachlorodisilane(Si₂Cl₆, abbreviation: HCDS) gas or the like is gas-phase decomposed. Onthe other hand, the SiCl₄ gas is not gas-phase decomposed even under ahigh temperature condition in which the DCS gas or the HCDS gas isgas-phase decomposed. Therefore, when performing the film-formingprocess at this relatively high temperature zone, it can be said thatthe SiCl₄ gas is a precursor capable of enhancing the thicknesscontrollability of the SiN film formed on the wafer 200.

In the case where the SiCl₄ gas is supplied to the wafer 200 from theside of the wafer 200 as in the present embodiment, there is a tendencythat the formation of the first SiN layer starts earlier in the outerperipheral portion of the wafer 200, and starts in the central portionof the wafer 200 with delay. This phenomenon becomes particularlyconspicuous when the aforementioned pattern is formed on the surface ofthe wafer 200. At this step, if the supply time of the SiCl₄ gas is lessthan 60 seconds, although the first SiN layer may be formed in the outerperipheral portion of the wafer 200, the first SiN layer may bedifficult to be formed in the central portion of the wafer 200. Bysetting the supply time of the SiCl₄ gas at a time of 60 seconds ormore, it is possible to form the first SiN layer substantiallyuniformly, i.e., substantially uniformly in thickness and composition,from the outer peripheral portion to the central portion of the wafer200. However, if the supply time of the SiCl₄ gas exceeds 180 seconds,the supply of the SiCl₄ gas to the wafer 200 may be continued in a statein which the formation reaction of the first SiN layer on the surface ofthe wafer 200 is saturated. As a result, the usage amount of the SiCl₄gas which does not contribute to the formation of the first SiN layerunnecessarily increases, which may increase the gas cost. By setting thesupply time of the SiCl₄ gas at a time of 180 seconds or less, it ispossible to suppress an increase in gas cost. By setting the supply timeof the SiCl₄ gas at a time of 120 seconds or less, it is possible toreliably suppress an increase in gas cost.

After the first SiN layer is formed on the wafer 200, the valve 243 a isclosed to stop the supply of the SiCl₄ gas into the process chamber 201.Then, the gas or the like remaining within the process chamber 201 isremoved from the interior of the process chamber 201 under the sameprocessing procedures and processing conditions as those of the purgestep of step A described above.

[Step C]

At this step, an NH₃ gas is supplied to the wafer 200 in the processchamber 201, i.e., the first SiN layer formed on the wafer 200.Specifically, the opening/closing control of the valves 243 b to 243 dis performed in the same procedure as the opening/closing control of thevalves 243 b to 243 d at step A. The flow rate of the NH₃ gas iscontrolled by the MFC 241 b. The NH₃ gas is supplied into the processchamber 201 via the nozzle 249 b and is exhausted from the exhaust pipe231. At this time, the NH₃ gas is supplied to the wafer 200 from theside of the wafer 200.

The processing conditions at this step may be exemplified as follows:

Supply time of NH₃ gas: 1 to 60 seconds, or 1 to 50 seconds in someembodiments.

Other processing conditions may be similar to the processing conditionsof step A.

By supplying the NH₃ gas to the wafer 200 under the aforementionedconditions, it is possible to react the SiCl termination formed on thesurface of the first SiN layer with NH₃. Specifically, at least aportion of N—H bonds in NH₃ and at least a portion of Si—Cl bonds in theSiCl termination formed on the surface of the first SiN layer can bebroken. Then, N after the at least a portion of N—H bonds in NH₃ arebroken can be bonded to Si after the at least a portion of Si—Cl bondsin the SiCl termination formed on the surface of the first SiN layer arebroken to form Si—N bonds. H separated from N and Cl separated from Sirespectively constitute gaseous substances such as HCl or the like so asto be desorbed from the wafer 200 and are exhausted from the exhaustpipe 231.

At this step, the N—H bonds, which are not converted into the Si—N bondsamong the N—H bonds in NH₃ during the aforementioned reaction, can beheld without being broken. That is, at this step, N after the at least aportion of N—H bonds in NH₃ are broken can be bonded to Si after the atleast a portion of Si—Cl bonds in the SiCl termination formed on thesurface of the first SiN layer are broken in a state in which H isbonded to each of two bonding hands among three bonding hands of Nconstituting NH₃.

In the present disclosure, the aforementioned reaction proceeding on thesurface of the wafer 200 at step C will be referred to as an adsorptivesubstitution reaction. At this step, the adsorptive substitutionreaction described above can go ahead to form a layer which contains Siand N and whose entire surface is terminated with NH, i.e., a siliconnitride layer (second SiN layer) having NH termination formed on itssurface, on the wafer 200. A partial enlarged view of the surface of thewafer 200 on which the second SiN layer having NH termination formed onits surface is formed is illustrated in FIG. 5C. Furthermore, the NHtermination formed on the surface of the second SiN layer may beregarded as synonymous with the H termination.

The processing conditions at this step are conditions under which onlythe adsorptive substitution reaction described above occurs on the wafer200. At this step, N after the at least a portion of N—H bonds in NH₃are broken can be bonded to Si after the at least a portion of Si—Clbonds in the SiCl termination formed on the surface of the wafer 200 arebroken in a state where H is bonded to each of two bonding hands amongthree bonding hands of N constituting NH₃.

In the case where the NH₃ gas is supplied to the wafer 200 from the sideof the wafer 200 as in the present embodiment, there is a tendency thatthe formation of the second SiN layer starts earlier in the outerperipheral portion of the wafer 200, and starts in the central portionof the wafer 200 with delay. This phenomenon becomes particularlyconspicuous when the aforementioned pattern is formed on the surface ofthe wafer 200. At this step, if the supply time of the NH₃ gas is lessthan 1 second, although the second SiN layer may be formed in the outerperipheral portion of the wafer 200, the second SiN layer may bedifficult to be formed in the central portion of the wafer 200. Bysetting the supply time of the NH₃ gas at a time of 1 second or more, itis possible to form the second SiN layer substantially uniformly, i.e.,substantially uniformly in thickness and composition, from the outerperipheral portion to the central portion of the wafer 200. However,when the supply time of the NH₃ gas exceeds 60 seconds, the supply ofthe NH₃ gas to the wafer 200 may be continued in a state in which theformation reaction of the second SiN layer on the surface of the wafer200 is saturated. As a result, the usage amount of the NH₃ gas whichdoes not contribute to the formation of the second SiN layerunnecessarily increases, which may increase the gas cost. By setting thesupply time of the NH₃ gas at a time of 60 seconds or less, it ispossible to suppress an increase in gas cost. By setting the supply timeof the NH₃ gas at a time of 50 seconds or less, it is possible toreliably suppress an increase in gas cost.

After the second SiN layer is formed on the wafer 200, the valve 243 bis closed to stop the supply of the NH₃ gas into the process chamber201. Then, the gas or the like remaining within the process chamber 201is removed from the interior of the process chamber 201 under the sameprocessing procedures and processing conditions of the purge step ofstep A described above.

As the second reaction gas, it may be possible to use, in addition tothe NH₃ gas, various kinds of hydrogen nitride-based gases exemplifiedat step A described above. Furthermore, it may be possible to usedifferent gases as the first reaction gas and the second reaction gas.For example, it may be possible to use the NH₃ gas as the first reactiongas and the N₂H₂ gas as the second reaction gas.

[Performing a Predetermined Number of Times]

After step A is performed, a cycle which non-simultaneously, i.e.,non-synchronously, performs steps B and C is implemented a predeterminednumber of times (n times, where n is an integer of 1 or more), whereby aSiN film having a predetermined thickness can be formed on the wafer200. The surface of the second SiN layer formed by performing step Cbecomes a surface terminated with NH, like the surface of the wafer 200after performing step A. That is, the surface of the wafer 200 afterperforming step C becomes a surface on which the first SiN layer is easyto be formed when performing step B thereafter. Therefore, the cyclewhich non-simultaneously performs steps B and C after performing step Acan be implemented a predetermined number of times to alternatelyperform the formation of the first SiN layer on the wafer 200 and theformation of the second SiN film on the wafer 200. As a result, theformation of the SiN film on the wafer 200 can go ahead with enhancedcontrollability. Furthermore, the aforementioned cycle may be repeatedmultiple times. That is, the thickness of the second SiN layer formedwhen the cycle which non-simultaneously performs steps B and C isimplemented once may be set smaller than a desired thickness, and theaforementioned cycle may be repeated multiple times until the thicknessof the SiN film formed by laminating the second SiN layer becomes equalto the desired thickness.

Furthermore, in order to allow the SiN film formed on the wafer 200 tobecome a film having excellent in-plane film thickness uniformity, it isdesirable that the supply time of the SiCl₄ gas at step B may be setsuch that the thickness of the first SiN layer formed in the centralportion of the wafer 200 becomes substantially equal to the thickness ofthe first SiN layer formed in the outer peripheral portion of the wafer200 in some embodiments. In other words, the supply time of the SiCl₄gas at step B may be set for a time so that the amount of the adsorptivesubstitution reaction occurring between the NH termination formed on thesurface of the wafer 200 and the SiCl₄ gas in the central portion of thewafer 200 becomes substantially equal to the amount of the adsorptivesubstitution reaction occurring between the NH termination formed on thesurface of the wafer 200 and the SiCl₄ gas in the outer peripheralportion of the wafer 200 in some embodiments. For example, by settingthe supply time of the SiCl₄ gas at step B longer than the supply timeof the NH₃ gas at step C, it is possible to reliably achieve theoperational effects described above.

Furthermore, in order to allow the SiN film formed on the wafer 200 tobecome a film having excellent in-plane film thickness uniformity, thesupply time of the NH₃ gas at step A may be set for a time so that theamount or density of the NH termination formed in the central portion ofthe wafer 200 becomes substantially equal to the amount or density ofthe NH termination formed in the outer peripheral portion of the wafer200 in some embodiments. For example, by setting the supply time of theNH₃ gas at step A longer than the supply time of the NH₃ gas at step C,it is possible to reliably achieve the operational effects describedabove. In addition, for example, by setting the supply time of the NH₃gas at step A longer than the supply time of the SiCl₄ gas at step B, itis possible to more reliably achieve the operational effects describedabove.

From this fact, the supply time of the NH₃ gas at step A may be setlonger than the supply time of the SiCl₄ gas at step B, and the supplytime of the SiCl₄ gas at step B may be set longer than the supply timeof the NH₃ gas at step C in some embodiments. By setting the supply times of the various kinds of gases at steps A, B, and C to have such abalance, it is possible to allow the SiN film formed on the wafer 200 tobecome a film having very excellent in-plane film thickness uniformity.

(After-Purge and Atmospheric Pressure Return)

After the aforementioned film-forming process is completed, the N₂ gasis supplied from the respective gas supply pipes 232 c and 232 d intothe process chamber 201 and is exhausted from the exhaust pipe 231.Thus, the interior of the process chamber 201 is purged and the gas orthe reaction byproduct, which remains within the process chamber 201, isremoved from the interior of the process chamber 201 (after-purge).Thereafter, the internal atmosphere of the process chamber 201 issubstituted by an inert gas (inert gas substitution). The internalpressure of the process chamber 201 is returned to an atmosphericpressure (atmospheric pressure return).

(Boat Unloading and Wafer Discharging)

Thereafter, the seal cap 219 is moved down by the boat elevator 115 toopen the lower end of the reaction tube 203. Then, the processed wafers200 supported on the boat 217 are unloaded from the lower end of thereaction tube 203 to the outside of the reaction tube 203 (boatunloading). The processed wafers 200 are discharged from the boat 217(wafer discharging).

(3) Effects According to the Present Embodiment

According to the present embodiment, one or more effects as set forthbelow may be achieved.

(a) By performing a cycle a predetermined number of times under thecondition where SiCl₄ is not gas-phase decomposed after performing stepA, the cycle including non-simultaneously performing step B and step C,it is possible to allow the SiN film formed on the wafer 200 to become afilm having excellent in-plane film thickness uniformity.

This is because, by performing step B under the aforementionedconditions, i.e., under the conditions in which only the adsorptivesubstitution reaction occurs between the NH termination formed on thesurface of the wafer 200 and SiCl₄, it is possible to allow the firstSiN layer formed on the wafer 200 to become a layer whose entire surfaceis terminated with SiCl. That is, it is possible to allow the first SiNlayer to become a layer to which self-limitation is applied for furtherSi adsorption reaction, i.e., for further adsorptive substitutionreaction. As a result, it is possible to allow the first SiN layerformed on the wafer 200 to become a layer having excellent in-planethickness uniformity. This also makes it possible to allow the secondSiN layer formed by modifying the first SiN layer to become a layerhaving excellent in-plane thickness uniformity at subsequent step C.

Furthermore, by performing step C under the aforementioned conditions,i.e., under the conditions in which only the adsorptive substitutionreaction occurs between the SiCl termination formed on the surface ofthe first SiN layer and NH₃, it is possible to allow the second SiNlayer formed on the wafer 200 to become a layer whose entire surface isterminated with NH. This makes it possible for the adsorptivesubstitution reaction between the NH termination formed on the surfaceof the second SiN layer and SiCl₄ to go ahead uniformly over the entiresurface of the wafer 200 at step B performed in the subsequent cycle. Asa result, it is possible to allow the first SiN layer formed on thesecond SiN layer to become a layer having excellent in-plane thicknessuniformity. This makes it possible to allow the second SiN layer formedby modifying the first SiN layer to become a layer having excellentin-plane thickness uniformity at subsequent step C.

As described above, according to the present embodiment, only the NHtermination formed on the wafer 200 and the SiCl termination formed onthe wafer 200 can be allowed to utilize a film-forming mechanism whichcontributes to the formation of the SiN film on the wafer 200. As aresult, it is possible to allow the SiN film formed on the wafer 200 tobecome a film having excellent in-plane film thickness uniformity.

(b) By setting the supply time of the SiCl₄ gas at step B longer thanthe supply time of the NH₃ gas at step C, it is possible to allow thefirst SiN layer having SiCl termination formed on its surface formed onthe wafer 200 to become a layer having excellent in-plane thicknessuniformity. As a result, it is possible to allow the SiN film formed onthe wafer 200 to become a film having excellent in-plane film thicknessuniformity.

(c) By setting the supply time of the NH₃ gas at step A longer than thesupply time of the NH₃ gas at step C, it is possible to uniformly formthe NH termination from the outer peripheral portion to the centralportion of the wafer 200. This makes it possible to allow the first SiNlayer formed on the wafer 200 to become a layer having excellentin-plane thickness uniformity at step B performed in the subsequentcycle. As a result, it is possible to allow the SiN film formed on thewafer 200 to become a film having excellent in-plane film thicknessuniformity.

In addition, by setting the supply time of the NH₃ gas at step A longerthan the supply time of the SiCl₄ gas at step B, it is possible to morereliably achieve the aforementioned effects.

(d) Since the SiCl₄ gas is used as the precursor, although step B isperformed under a relatively high temperature condition (temperaturecondition of 700 degrees C. or higher) in which the DCS gas or HCDS gasis gas-phase decomposed, it is possible to allow the thickness of thefirst SiN layer to become a uniform thickness of less than one atomiclayer (less than one molecular layer) over the entire region in theplane of the wafer. Therefore, it is possible to precisely and stablycontrol the thickness of the SiN film. That is, it is possible to allowthe formation of the SiN film on the wafer 200 to go ahead with enhancedcontrollability.

Furthermore, when the DCS gas or HCDS gas is used as the precursor, forexample, under a relatively high temperature condition of 700 degrees C.or higher, the precursor is vapor-phase decomposed and the Si-containinglayer formed on the wafer 200 by supplying the precursor becomes a layerto which self-limitation is not applied for further Si adsorptionreaction. Therefore, it is difficult to allow the thickness of theSi-containing layer formed by supplying these precursors to become auniform thickness of less than one atomic layer (less than one molecularlayer) over the entire region in the plane of the wafer under arelatively high temperature condition. As a result, it is difficult toprecisely and stably control the thickness of the finally obtained SiNfilm.

(e) The effects mentioned above can be similarly achieved in the casewhere the aforementioned hydrogen nitride-based gas other than the NH₃gas is used or in the case where the aforementioned inert gas other thanthe N₂ gas is used, as the first and second reactants. In addition, theeffects mentioned above can be similarly achieved in the case wheredifferent hydrogen nitride-based gases are used as the first and secondreactants.

Other Embodiments

While one embodiment of the present disclosure has been specificallydescribed above, the present disclosure is not limited to theaforementioned embodiment but may be variously modified withoutdeparting from the spirit of the present disclosure.

At least one of step A and step C, the NH₃ gas activated by plasma maybe supplied to the wafer 200. Even in this case, the same effects asthose of the film-forming sequence illustrated in FIG. 4 may beachieved.

Recipes used in substrate processing may be prepared individuallyaccording to the processing contents and may be stored in the memorydevice 121 c via a telecommunication line or an external memory device123. Moreover, at the start of substrate processing, the CPU 121 a mayproperly select an appropriate recipe from the recipes stored in thememory device 121 c according to the processing contents. Thus, it ispossible for a single substrate processing apparatus to form films ofdifferent kinds, composition ratios, qualities and thicknesses withenhanced reproducibility. In addition, it is possible to reduce anoperator's burden and to quickly start the substrate processing whileavoiding an operation error.

The recipes mentioned above are not limited to newly-prepared ones butmay be prepared by, for example, modifying the existing recipes alreadyinstalled in the substrate processing apparatus. When modifying therecipes, the modified recipes may be installed in the substrateprocessing apparatus via a telecommunication line or a recording mediumstoring the recipes. In addition, the existing recipes already installedin the substrate processing apparatus may be directly modified byoperating the input/output device 122 of the existing substrateprocessing apparatus.

In the aforementioned embodiment, there has been described an example inwhich films are formed using a batch-type substrate processing apparatuscapable of processing a plurality of substrates at a time. The presentdisclosure is not limited to the aforementioned embodiment but may beappropriately applied to, e.g., a case where films are formed using asingle-wafer-type substrate processing apparatus capable of processing asingle substrate or several substrates at a time. In addition, in theaforementioned embodiments, there have been described examples in whichfilms are formed using the substrate processing apparatus provided witha hot-wall-type process furnace. The present disclosure is not limitedto the aforementioned embodiments but may be appropriately applied to acase where films are formed using a substrate processing apparatusprovided with a cold-wall-type process furnace.

In the case of using these substrate processing apparatuses, afilm-forming process may be performed by the processing procedures andprocessing conditions similar to those of the embodiments andmodifications described above. Effects similar to those of theembodiments and modifications described above may be achieved.

The embodiments, modifications and the like described above may beappropriately combined with one another. The processing procedures andprocessing conditions at this time may be similar to, for example, theprocessing procedures and processing conditions of the aforementionedembodiment.

EXAMPLES First Example

In example 1, a film-forming process of forming a SiN film on a waferwas performed a plurality of times using the substrate processingapparatus illustrated in FIG. 1 and by the film-forming sequenceillustrated in FIG. 4. The film-forming temperature was set at 650degrees C., 700 degrees C., 750 degrees C., and 800 degrees C. Otherprocessing conditions were set to predetermined conditions which fallwithin the processing condition range of the aforementioned embodiments.

In comparative example 1, after performing step A of the film-formingsequence illustrated in FIG. 4 to form NH termination on the wafer usingthe substrate processing apparatus illustrated in FIG. 1, a cycle isperformed a predetermined number of times, the cycle includingnon-simultaneously performing a step B′ of supplying a DCS gas to awafer and a step C′ of supplying an NH₃ gas to the wafer, whereby afilm-forming process of forming a SiN film on the wafer was performedmultiple times. The film-forming temperature was set at 550 degrees C.,600 degrees C., 650 degrees C., and 700 degrees C. The processingconditions at steps A, B ‘and C’ were set similar to the processingconditions of steps A to C of the example, respectively.

Then, the in-plane film thickness uniformities of the SiN film formed inexample 1 and comparative example 1 were each measured. The measurementresults are shown in FIG. 6A.

The vertical axis in FIG. 6A indicates an in-plane film thicknessuniformity (%) of the SiN film. When the value of the in-plane filmthickness uniformity (%) is 0, it means that the film thickness of theSiN film is uniform from the central portion to the outer peripheralportion of the wafer. When the value of the in-plane film thicknessuniformity (%) is larger than 0, it means that the thickness of the SiNfilm has a distribution which is the largest in the central portion ofthe wafer surface and is gradually decreased toward the outer peripheralportion thereof, i.e., a central convex distribution. When the value ofthe in-plane film thickness uniformity (%) is smaller than 0, it meansthat the thickness of the SiN film has a distribution which is thelargest in the outer peripheral portion of the wafer surface and isgradually decreased toward the central portion thereof, i.e., a centralconcave distribution. In addition, the value of the in-plane filmthickness uniformity (%) indicates that the in-plane film thicknessuniformity of the SiN film formed on the wafer is better as itapproaches zero. The horizontal axis in FIG. 6A indicates a film-formingtemperature (degrees C.) when forming the SiN film. In FIG. 6A, thesymbol ● indicates example 1 and the symbol X indicates comparativeexample 1.

According to FIG. 6A, it can be seen that the in-plane film thicknessuniformity of the SiN film in example 1 is consistently excellentregardless of the film-forming temperature. In contrast, it can be seenthat the in-plane film thickness uniformity of the SiN film incomparative example 1 varies greatly from the central convexdistribution to the central concave distribution as the film-formingtemperature increases. It is also understood that the in-plane filmthickness uniformity of the SiN film in the comparative example shows astrong central concave distribution when the film-forming temperatureexceeds 650 degrees C. That is, under a temperature condition of a hightemperature exceeding at least 650 degrees C., it is understood that itis possible to more improve the in-plane film thickness uniformity ofthe SiN film by using the SiCl₄ gas as the precursor instead of usingthe DCS gas as the precursor.

In addition, a wet etching rate (hereinafter, referred to as a WER) ofthe SiN film formed in each of example 1 and comparative example 1 wasmeasured, and each processing resistance was evaluated. The measurementresults are shown in FIG. 6B.

The vertical axis in FIG. 6B indicates a WER (Å/min) of the SiN filmwith respect to hydrofluoric acid have a concentration of 1% (1% HFaqueous solution). The horizontal axis in FIG. 6B indicates comparativeexample 1 and example 1 in order. Comparative example 1 is a SiN filmformed at a film-forming temperature of 650 degrees C., and example 1 isa SiN film formed at a film-forming temperature of 800 degrees C.

According to FIG. 6B, it can be seen that a WER (6.2 Å/min) of the SiNfilm of example 1 is smaller than a WER (9.7 Å/min) of the SiN film ofcomparative example 1. That is, it can be seen that the SiN film formedusing the SiCl₄ gas as the precursor under a relatively high temperaturecondition has better processing resistance (wet etching resistance) thanthe SiN film formed using the DCS gas as the precursor under arelatively low temperature condition.

Example 2

In example 2, a SiN film was formed on a wafer using the substrateprocessing apparatus illustrated in FIG. 1 and by the film-formingsequence illustrated in FIG. 4. A bare wafer on which no pattern wasformed and a pattern wafer on which a pattern is formed and which has asurface area 50 times the surface area of the bare wafer were used asthe wafer. The processing condition at each step were set topredetermined conditions which fall within the processing conditionrange of the aforementioned embodiments.

In comparative example 2, after performing step A of the film-formingsequence illustrated in FIG. 4 to form NH termination on the wafer usingthe substrate processing apparatus illustrated in FIG. 1, a cycle isperformed a predetermined number of times, the cycle includingnon-simultaneously performs a step B′ of supplying a DCS gas to thewafer and a step C′ of supplying an NH₃ gas to the wafer at, whereby aSiN film was formed on the wafer. The bare wafer and the pattern waferdescribed above were each used as the wafer. The processing conditionsat steps A, B′ and C′ were set similar to the processing conditions atsteps A to C of the example, respectively.

Then, the in-plane film thickness uniformities of the SiN film formed inexample 2 and comparative example 2 were each measured. The measurementresults are shown in FIG. 7. The vertical axis in FIG. 7 indicates anin-plane film thickness uniformity (%) of the SiN film, and meaning ofits value is similar to the vertical axis in FIG. 6A. The horizontalaxis in FIG. 7 indicates a case where the bare wafer is used as thewafer and a case where the pattern wafer is used as the wafer. In FIG.7, a white columnar graph shows comparative example 2 and a shadedcolumnar graph shows example 2.

According to FIG. 7, it can be seen that the in-plane film thicknessuniformity of the SiN film in example 2 is excellent both in the casewhere the bare wafer is used as the wafer and in the case where thepattern wafer is used as the wafer. In contrast, it can be seen that thein-plane film thickness uniformity of the SiN film in comparativeexample 2 shows a strong central convex distribution when the bare waferis used as the wafer and a strong central concave distribution when thepattern wafer is used as the wafer. That is, it can be seen that theinfluence of the SiN film in example 2 on the in-plane film thicknessuniformity due to the surface area of the wafer can be suppressed to besmaller than that on the SiN film in comparative example 2. In otherwords, it can be seen that the film-forming method in example 2 cansuppress a so-called loading effect (substrate surface area dependency)to be smaller than that of the film-forming method in comparativeexample 2.

According to the present disclosure in some embodiments, it is possibleto improve film thickness uniformity of a SiN film formed on thesubstrate in the plane of the substrate.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the disclosures. Indeed, the embodiments described herein maybe embodied in a variety of other forms. Furthermore, various omissions,substitutions and changes in the form of the embodiments describedherein may be made without departing from the spirit of the disclosures.The accompanying claims and their equivalents are intended to cover suchforms or modifications as would fall within the scope and spirit of thedisclosures.

What is claimed is:
 1. A method of manufacturing a semiconductor device.